This invention relates in general to an improved running tool, and in particular to an improved running tool for soft landing a tubing hanger in a wellhead housing.
Designs for landing tubing hangers in casing hangers for wells in the ocean floor are well known in the prior art. A tubing hanger typically carries or suspends one or more strings of tubing which extend down into the subsea well. Many different tubing hanger designs exist and are the subject of numerous prior art patents. Some of the earlier versions of tubing hangers required a running tool employing a dart for operation that restricted the bore of the tubing hanger. Other designs provide a running tool allowing full bore tubing access during running, while providing means for controlling downhole safety valves during both running and landing operations.
For example, in U.S. Pat. No. 4,067,062, the tubing hanger is lowered into the well and releasably secured to the casing hanger by hydraulic manipulation of the running tool after the tubing hanger has been oriented in the casing hanger. After further hydraulic manipulation, the running tool may be released from the hydraulic set tubing hanger and later run back into the well and reconnected to the tubing hanger for retrieval. Although each of these designs are workable, it is difficult to avoid xe2x80x9chardxe2x80x9d landing and possibly damaging the tubing hanger in the well due to the depths at which the subsea wells are typically located. Thus, an improved design for xe2x80x9csoftxe2x80x9d landing a tubing hanger in a wellhead is needed.
In one embodiment of the present invention, a running tool for a tubing hanger has multiple passages with respective chambers. The running tool has an outer sleeve, a piston, and an inner sleeve in their upper positions such that a pair of collets are released from a tubing hanger and the running tool is detached from the tubing hanger. After a horizontal production tree is installed on the wellhead, the operator connects a string of tubing and the running tool to the tubing hanger. When pressure is applied to an upper inner sleeve chamber and released from a lower inner sleeve chamber, the inner sleeve moves down to capture the collets and engage the tubing hanger. The operator runs the assembly into the well.
The upper inner sleeve chamber is initially pressurized and the outer sleeve chamber is locked so that the running tool can be hard-landed in the bore. When the outer sleeve lands in the bore, the impact is absorbed by the running tool, not by the tubing hanger. After the running tool has landed, fluid in the outer sleeve chamber is bled off so that the running tool descends axially relative to the outer sleeve. This process is gradual so that the tubing hanger is landed softly. Next, the piston is forced downward to actuate the lower sleeve, thereby moving locking means into a bore profile to secure the tubing hanger.
After the tubing hanger is landed, the running tool is retrieved by pressurizing the lower inner sleeve chamber and releasing pressure from the upper inner sleeve chamber and the piston chamber to lift the inner sleeve. This action releases the collets to detach the running tool from the tubing hanger. The running tool is then brought back to the surface without the tubing hanger, which remains landed in the bore. At the surface, the inner sleeve is already in the upper position, so the outer sleeve chamber and the upper inner sleeve chamber are re-pressurized to reset the running tool for another job.